1. Field of the Invention
The present invention relates to a dielectric resonator and a dielectric filter suitable for use in an electronic device such as a shared device of transmission and reception signals (duplexer) for a cellular base station.
2. Description of the Related Art
As shown in FIG. 9, generally, a conventional dielectric resonator is constructed in such a manner that a cylindrical dielectric block 100 made of ceramics is fixed on the bottom of a metal casing body 101 and the opening of the metal casing body 101 is covered with a casing lid 101a for keeping an electromagnetic field energy inside.
An input connector 102 is attached to, for example, the left-side wall of the metal casing body 101 and an output connector 103 is attached to the right-side wall. The front ends of central conductors 102a and 103a of the input and output connectors 102 and 103 penetrate the left-side and right-side walls, respectively, and are projected to the inside of the metal casing body 101. One ends of coil-shaped coupling loops 104 and 105 are soldered to the front ends of the central conductors 102a and 103a, respectively. The other ends of the coupling loops 104 and 105 are fixedly soldered to the metal casing body 101 and connected to the ground.
According to another conventional example, as shown in FIG. 10, one ends of almost linear probes 114 and 115 are connected to the central conductors of input and output connectors 112 and 113, respectively, which project to the inside of a metal casing 111, the probes 114 and 115 are arranged along the internal circumferencial wall of the metal casing 111, and the other ends are disposed near the dielectric block 100.
In a dielectric resonator having such a construction, the coupling loops 104 and 105 or the probes 114 and 115 are magnetically coupled to the dielectric block 100. When an electric signal is supplied to the coupling loop 104 or the probe 114, a magnetic field is produced in the coupling loop 104 or the probe 114. By the magnetic energy, the dielectric block 100 is excited, a current is passed through the dielectric block 100, and a magnetic field is produced. By the magnetic energy, a magnetic field is generated, a current is passed through the coupling loop 105 or the probe 115 on the output side, and an electric signal is outputted from the output side connector 103 or 113.
In a conventional dielectric resonator as described above, the coupling loops 104 and 105 or the probes 114 and 115 a re not structurally resistant to vibration. When the dielectric resonator is subjected to vibration, the coupling loops 104 and 105 or the probes 114 and 115 vibrate more than the dielectric resonator 100. Consequently, there is an inconvenience such that the degree of coupling to the dielectric block 100 changes.
In order to deal with it, a method of fixing the coupling loops 104 and 105 or the probes 114 and 115 so as not to vibrate by using an adhesive such as paraffin can be considered. However, a problem such that deterioration in performance occurs due to the application of the adhesive arises.